Distribution Status of the Cotton Rat (Sigmodon hispidus) in Colorado

Abstract

The hispid cotton rat (Sigmodon hispidus) was first reported in Colorado when Goldman and Gardner (J. Mamm., 28:57-59, 1947) reviewed a series of 13 specimens collected by Alfred M. Bailey in 1946 from a site 11 mi. N Springfield, Baca County. Hansen (J. Mamm., 44:126, 1963) recorded a specimen from 18 mi. N Lamar in Kiowa County. Armstrong (Monogr., Univ. Kansas Mus. Nat. Hist., 3:x + 1-415) summarized the known distribution to include additional specimens from Bent (2 mi. S, 2 mi. E Hasty), Baca (Two Buttes Reservoir; 14 mi. N, 4 mi. E Springfield; 6 mi. W Williams' Corner; I. N. Pruitt Farm, near Williams' Corner, 11 mi. N Springfield), and Cheyenne (5 mi. E Kit Carson) counties. Subsequently, Carey (J. Mamm., 59:624, 1978) collected cotton rats near the Pueblo Army Depot northwest of Boone in Pueblo County. Additional specimens, herein reported, were collected by personnel from the Museum of the High Plains (MHP) from Baca and Pueblo counties as well as the first record from Otero County. Some of those specimens are housed in the National Fish and Wildlife (NFW) collection in Fort Collins. Unreported specimens collected in 1970 (Jim Fitzgerald, pers. comm.) and housed at the University of Northern Colorado (UNC) are also noted. Specimens examined, 36, distributed as follows: BACA COUNTY: 61/4 mi. S, 91/2 mi. W Campo, 1 (MHP); 4V2 mi. S Vilas, 1 (MHP); CROWLEY COUNTY: 3 mi. E Sugar City, 6 (UNC); PUEBLO COUNTY: 3 mi. N, 93/4 mi. W Goodnight, 11 (NFW); 23/4 mi. N, 73/4 mi. W Goodnight, 1 (NFW); 31/2 mi. N, 103/4 mi. W Goodnight, 2 (NFW); 3 mi. N, 9 mi. W Goodnight, 2 (NFW); 21/2 mi. N, 83 /4mi. W Goodnight 6 (3 NFW, 3 MHP); OTERO COUNTY: 153/4 mi. S, 4 mi. E La Junta, 2 (MHP). It should be noted that all specimens in southeastern Colorado have been collected on or near tributaries of the Arkansas and Cimarron rivers. There are two possibilities to explain the current distribution of cotton rats in southeastern Colorado. The first is dispersal from surrounding states. Dispersal might have occurred from western Kansas along riparian habitats afforded by the Arkansas and Cimarron rivers and their tributaries or it might have occurred northward into Colorado from New Mexico along